Round Belt Pulley Creator

This thing generates pulleys for round belts (and ropes).
You create any size pulley, with or without a hub, for round belts of any size.
You can have any number of belts
Your pulley can have zero to four mounting screws, with or without nut traps.
The axel hole can be any size.
You can create smooth wheels (no belts) or with any number of grooves. Using 1 or more round belts or O-rings creates a wheel with a tire.

You may want to check out my closely related thing for creating round belt pulleys. (https://www.thingiverse.com/thing:3013839)

Thingiverse Customizer sometimes seems to refuse to run. (It probably takes a lot of computer resources to Customize files for everyone in the world.) A workaround is to download the OpenSCAD application and process the .scad file on your own machine. I have posted a brief guide. http://bit.ly/openscad-at-home

UPDATE 1-- July 31, 2018 -- Posted updated file that corrects an error in calculating the pulley diameter. (Squashed a gremlin that had been creating a pulley diameter that was ½ the belt diameter too small.)
UPDATE 2 -- August 17, 2018 Redesigned the bottom of the nut trap for hex nuts to create a better fit.